Fens

Fen
Courtesy EPA ©

Fens are peatlands that formed from vegetation receiving a constant supply of base-rich groundwaters and therefore can be described as minerotrophic (fed by groundwater). Fen peats in Ireland have usually a relatively high pH. Fen peats are mineral rich, with a relatively high ash content (10–20%) and a relatively shallow peat depth (c. 2 m). The vegetation is generally species rich and largely contains tall herbs, rushes and grasses, with brown mosses a feature of the ground layer.

While a fen can be seen as a transitional ecosystem enroute to becoming a raised bog, they rarely progress in this natural direction due to human-induced influences, be it reclamation for agriculture, roadworks or landfilling. Natural fens are rare, as 97% of the country’s fens have been drained for agriculture. Fens are the least protected peatland types in Ireland. They have the lowest protected area with only 37 sites designated as Special Areas Of Conservation (SACs) (Irish Peatland Conservation Council, n.d.). While fens of conservational importance still occur right across the country, their current extent is estimated at 20,180 ha (EPA, 2011). This compares with an original extent of 92,508 ha (Irish Peatland Conservation Council, n.d.). For further information on the conservation status of fens, visit the Irish Peatland Conservation Council website.